Numerical analysis of plasmonic nanostar-whispering gallery mode hybrid microresonator

Abstract

The ultra-sensitive real time detection and exotic manipulation of single biomolecules find its application in diverse fields of science and medicine especially in new generation integrated diagnostic assays. In this backdrop, with their very high quality factors, the whispering gallery mode (WGM) microresonators have attracted the prominence due to their ultra-sensitive label-free detection capabilities where high precision biosensing is demanded [1]. In the recent past combining the field enhancing resonant properties of plasmonic nanoparticles, hybrid-WGM microresonators with huge field enhancement factors have been reported [1-3]. Here we present our computational investigations on plasmonic nanostar-WGM hybrid microresonators envisaged for ultrasensitive real time diagnostic platform for biomolecules. The lightning rods of plasmonic nanostars with multiple branched spikes highly enhance the electromagnetic field [4, 5]. Unlike the residual surface roughness, the controlled tailoring of the sharp multiple branches in plasmonic nanostars could deterministically influence the field enhancement in such hybrid micrioresonators. We give numeric FEM 3D analysis (using COMSOL 5.2a) of the plasmonic nanostars-WGM hybrid microresonators. The numerical modelling of the nanostars and their extinction cross section analysis (Fig 1a) are investigated. The influence of core radius, spike length and width aspect ratios on the plasmon band shift is studied and applied for the realization of practically feasible plasmonic nanostar-WGM microresonators.